Author(s): Šekler M, Ašanin Ružica, Krnjaić D, Palić T, Milić N, Jovanović Tanja, Kovačević Dragana, Plavšić B, Stojanović Dragica, Vidanović D, Ašanin N
Keywords:avian influenza virus, wild birds, AGP, HI, ELISA
Infections caused by the avian influenza virus have been known for a long time and they are present, to a smaller or greater extent, in both extensive and intensive poultry production in many parts of the world. Epidemiological investigations have established a definite significance of the population of wild birds in maintaining and spreading this infection. Avian influenza is a zoonosis, and the virus has a great potential for causing mortality in humans, in particular its subtypes H5 and H7, which is why it has lately been provoking much attention among scientists and experts, as well as the general public. The objective of the work was to catch a certain number of wild birds in several locations in the Republic of Serbia, to identify them, and to collect samples of their blood serum for the determination of specific antibodies against the avian influenza virus. Birds were caught in ten locations in a manner that was safe for the birds themselves, as well as for the staff that did the catching. The birds were caught in especially produced nets, and in some cases in special traps. The caught wild birds were identified using the methods described in reference literature. All the names of the wild birds were coordinated with the valid Serbian nomenclature of European birds, prepared by prominent ornithologist and bird lover Milan Ru`i}. Following catching and identification, blood samples were taken from the birds from the wing vein (in bigger birds) or from the leg vein (in smaller birds). In taking blood samples from wild birds, all the principles of asepsis and antisepsis were followed in order to prevent any possibility of infection. After that, the birds were returned to their natural habitat, to the same locations in which they were caught. Serums were isolated from the taken blood samples and they were stored at -20oC until the final examinations. A total of 46 species of wild birds were identified among a total of 259 birds from which 259 samples of blood serum were isolated. The following were used for the detection of the presence of specific antibodies against the avian influenza virus in blood serum samples of wild birds: agar gel precipitation (AGP), the hemagglutination inhibition test (HI) for subtypes H5 and H7, the cELISA test with antigen for the A type avian infleunza virus, and the cELISA test with antigen for subtype H5 of the avian influenza virus. Due to the fact that about 360 different species of wild birds live in the Republic of Serbia, the number of 46 identified species covered by these investigations account for 12.77% of the total number of bird species present in Serbia, which is considered a good sample. Specific antibodies against the A type avian influenza virus were established in serum samples of only 9 of the 259 birds covered by examinations using the cELISA test. Of the 46 identified wild bird species, 6 belonged to birds that live exclusively in water habitats and are considered a reservoir of the avian influenza virus (white stork, mallard, mute swan, common pochard, common goldeneye, and Eurasian coot). Among the listed species, particular attention was drawn to 4 species of wild birds of the order Anseriformes and the family Anatidae (mallard, mute swan, common pochard, common goldeneye) of which there were 30 birds among the total of 259 examined. In the 30 blood serum samples of the listed bird species, specific antibodies against the A type avian influenza virus were established in 9 (30%) serum samples using cELISA. Specific antibodies against the avian inluenza virus subtype H5 were established in 3 serum samples of mute swans (one serum sample originated from a mute swan which was tagged in Poland) and in one blood serum sample of a common pochard, or a total of 4 (13.33%) serum samples, using the hemagglutination inhibition test. Specific antibodies against the avian inluenza virus subtype H7 were established in 3 (10%) blood serum samples, in two serum samples from mallards and one sample from a mute swan, using the hemagglutination inhibition test. Specific antibodies against the avian inluenza virus type A were not established in any examined bird species using the AGP test. In the population of wild bird species in the Republic of Serbia covered by these investigations, specific antibodies against the avian influenza virus were established only in serum samples of birds of the family Anatidae. Specific antibodies against the avian inluenza virus type A established in 3 (6.52%) species of wild birds, and against subtypes H5 and H7 in 2 (4.34%) of the total of 46 examined species. The sensitivity of the cELISA test for the avian inluenza virus subtype H5 and the hemagglutination inhibition test for subtype H5 amounted to 100%.
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